As children we must learn about mundane concepts like cats, balloons and chocolate. However, as experts we must learn extremely complex concepts. For example, dermatologists must learn difficult distinctions between skin maladies. Regardless of the expertise level, however, all concept learning involves extracting the relevant and disregarding irrelevant information. The three proposed experiments will reveal in detail exactly how categorizers apply selective attention to concepts. In particular, they will tell us how people selectively attend, what types of information they prefer to use to form concepts, under what circumstances they are able to fully disregard irrelevant information; how they go about discovering irrelevant information. Dynamics of selective attention will be related to the different strategies using eyetracking techniques. Eyetracking is new to categorization research and serves as a relatively direct measure of selective attention dynamics. Because models will be tested directly, the research will advance concept theory with a new source of data. This knowledge will help the healthy and those with learning disabilities discover techniques to overcome difficulties in acquiring new knowledge.